In an orthogonal frequency division multiplexing (OFDM) technology, a channel is divided into several orthogonal sub-channels, a high-rate data signal is converted into a parallel low-rate sub data stream and modulated to each sub-channel for transmission. Currently, the OFDM technology is widely applied to the broadcast audio and video field and the civil communications system, and main applications include: asymmetric digital subscriber loop (ADSL), ETSI standard digital audio broadcasting (DAB), digital video broadcasting (DVB), high definition television (HDTV), a wireless local area network (WLAN), and the like.
In a process of information transmission by means of the orthogonal frequency division multiplexing (OFDM), information needs to be modulated to an optical comb line generated by a transmitter, to form a multi-waveband signal, and signal demodulation is implemented at a receive end by using beat frequency between an optical comb in a receiver and the optical comb line generated by the transmitter. The optical comb line spacing in the transmitter and the optical comb line spacing in the receiver are not exactly the same and an offset exists between them; however, because the spacings are different, performance of the receiver is deteriorated. In the prior art, frequency offset compensation is usually performed on a radio frequency drive signal that is used to generate the optical comb line; however, the existing compensation method has relatively low accuracy.